Carton wax composition



Unite CARTON WAX COMPOSITION N Drawing. Application May 23, 1956 Serial No. 586,632

Claims priority, application Great Britain May 26, 1955 6 Claims. (Cl. 196-149) This invention relates to a wax composition for use in coating paperboard cartons for fruit juice.

The provision of a satisfactory coating for fruit juice cartons has hitherto been difficult owing to the low surface tension of fruit juices. Thus wax compositions which are satisfactory in producing leak-proof cartons for milk or even plain water are not generally satisfactory, in economic amounts, for producing leak-proof cartons for fruit juice. Fruit juice cartons at present manufactured are usually coated with a wax composition containing a proportion of polyethylene and the presence of the latter compound increases the cost of the composition considerably.

The principal object of the present invention is to provide a coating composition for cartons which has a high resistance to fruit juice absorption and which is cheaper than existing compositions containing polyethylene.-

According to the invention, a wax composition for coating cartons consists of a blend of 30-80% by weight of l25-l3-0 F. melting point grade (as determined by IP method 55 or ASTM method D87), substantially oilfree parafiin wax, and 7020% by weight of recrystallized bright stock wax, the recrystallized bright stock wax containing -40% by weight of petroleum ceresin wax and 13% by weight of oil (i. e. material as determined by ASTM method D721 The parafi'in wax should preferably be one having a fairly lwide boiling point spread i. e. greater than 100 F.

Preferably the amount of petroleum ceresin wax in the recrystallized bright stock wax is 20-25% by weight.

Most advantageously the amount of oil in the recrystallized bright stock wax should be 2% by weight.

Recrystallized bright stock wax is prepared from the residue left in the vacuum distillation of crude petroleum oil, which residue is used in the production of bright stock lubricating oil. The residue, after the removal of asphaltic material by treatment with propane, is crystallized firstly at a temperature below 0' F. and the slack or crude wax which is separated is recrystallized at a temperature in the range 3060 F The solvent used for this purpose is preferably methyl ethyl ketone/toluene. The crude oil used for the preparation of the recrystallized bright stock wax used in the blend according to the invention should be one containing petroleum ceresin wax.

The term petroleum ceresin wax, when used in the specification and claims, means the hard, brittle, highboiling microcrystalline waxes of the ceresin type which are found in many crude petroleum oils e. g. Middle Eastern crude oils and which may be separated from the remainder of the recrystallized bright stock wax by a further crystallization at 95-110 F.

The success of the blend according to the invention when used for coating fruit juice cartons is believed to be due to its .wide crystal side spread. The parafiin wax component of the blend consists of large crystals. The

tatcs Patent ice recrystallized bright stock wax component, when pre pared as described above, is largely microcrystalline i1 structure and contains a plastic wax (commonly known a petrolatum-typewax), petroleum ceresin Wax and a smal proportion of. oil. The petroleum ceresin wax can b separated from the plastic wax and oil by further re crystallizing the recrystallized bright stock wax at a tern perature of -l00 F. and each of these waxes in blent With parafiin wax shows good resistance to fruit juic absorption but neither blend is satisfactory for cal-to: manufacture. Thus a blendof' paraflin wax and plasti wax is difiicult to apply to cartons owing to its rela tively low congealing point and a blend of parafiin 'wa and petroleum ceresin waxis too brittle for carton manu facturer. The blend according to the invention, how ever, does not suffer from the above drawbacks. Th presence of a small proportion of oil in the recrystal lized bright stock wax improves the flexibility of .th final blend and therefore makes it less likely to crac when it is applied to cartons. It is not'usually necessar to add any oil separately since the recrystallized brigh st'o'c'k wax, when prepared as described above, alway contains a small proportion of oil. Likewise the neccs sary petroleum ceresin wax will always be persent i the recrystallized bright stock wax if it is prepared fror a suitable crude oil.

Table 1 compares the orange juice resistance of strip of carton paper which have been impregnated with para: fin wax and various wax blends. The application of th wax to the strips was done by immersing the strips i molten wax and subsequently allowing them to drain i an oven. The recrystallized bright stock wax was pre pared from a deasphalted Middle Eastern crude oil residu as described above, the crystallizations being from meth ethyl ketone/toluene at temperatures of 20? F. an 40 F. respectively. The plastic and petroleum ceresi waxes were prepared from the recrystallized bright stoc wax by a further crystallization at 95 F. in this par ticular case the petroleum ceresin wax amounted t 20-25% by weight of the recrystallized bright stock wa:

It will be seen that the blend according to the inver tion (blend F) has superior orange juice resistance to a other blends except the parafiin wax petroleum ceresi blend (blend D), but this latter blend is unsuitable fc carton manufacture for the reason given previously.

Table 1 Wax/waxed Orange Wax paper ratio, juice abpercent sorbed in wt./wt. hours, m

A. Paraflin wax /130 grade 35. 4 1 B. 89% wt. 125/130 grade parafiin wax +11% wt. commercial additive consisting of microcrystalline wax and polyethylene (2% polyethylene in final blend) 35.0 1 O. 70% wt. 125/130 grade paraffin wax +30% wt. plastic wax 34. 7 D. 70% wt. 125/130 grade paralfin wax +30% wt. petroleum ceresin wax 36. 1 E. 88% wt. 125/130 grade paraffin wax +10% wt. recrystallized bright stock wax +2% polyethylene -1 38. 6 1 F. 70% wt. 125/130 grade parafiin wax +30% wt. recrystallized bright stock wax 35. 4

Table 2 gives the results of storage tests on cartot filled with orange juice. The cartons were all waxed wit the 70/ 30 wt./ wt. paraffin wax/recrystallized bright stoc wax blend (blend 'F), and it will be seen that in Ol'dt to produce a. satisfactory carton the amount of wax c the carton must exceed a certain fairly critical amoun Table 2 Time for Wax/waxed carton ratio, percent wtJwt. leaks to appear, days We claim:

1. A wax composition consisting of a blend of 3080% wy weight of 125-130 F. melting point grade, substanially oil-free paraifin wax, and 7020% by weight of ecrystallized bright stock wax, the recrystallized bright tock wax containing 540% by weight of petroleum :eresin wax and 13% by weight of oil. i

2. A wax composition according to claim 1, in which he paraifin wax is one having a boiling-point spread of Lt least 100 F. I

3. A wax composition according to claim 1, in which he recrystallized bright stock wax contains 20-25% y weight of petroleum ceresin wax.

4. A wax composition according to claim 1, in which References Cited in the file of this patent UNITED STATES PATENTS 2,000,427 Tears May 7, 1935 2,127,668 Adams et al Aug. 23, 1938 2,654,692 Kiersted et a1. Oct. 6, 1953 2,773,812 Tench Dec. 11, 1956 OTHER REFERENCES Jenkins et :11: Modern Wax Technology (Journal of Chemical Education), April 1949, pp. 182-186.

\Minchin: Petroleum Waxes (Institute of Petroleum Review), October 1953, vol. 7, No. 82, pp. 321-328. 

1. A WAX COMPOSITION CONSISTING OF A BLEND OF 30-80% BY WEIGHT 125-130*F. MELTING POINT GRADE, SUBSTANTIALLY OIL-FREE PARAFFIN WAX, AND 70-20% BY WEIGHT OF RECRYSTALLIZED BRIGHT STOCK WAX, AND THE RECRYSTALLIZED BRIGHT STOCK WAX CONTAINING 5-40% BY WEIGHT OF PETROLEUM CERESIN WAX AND 1-3% BY WEIGHT OF OIL. 